From Wikipedia, the free encyclopedia

A GPS sonde, approx
220x80x75mm. (with Grounding Station in background, used to perform
a 'ground check' and also recondition the humidity sensor)

A radiosonde (Sonde is French for
probe) is a unit for use in weather balloons that measures various
atmospheric parameters and transmits them
to a fixed receiver. Radiosondes may operate at a radio frequency
of 403 MHz or 1680 MHz and both types may be
adjusted slightly higher or lower as required. A
rawinsonde is a radiosonde that is designed to
also measure wind speed and direction. Colloquially, rawinsondes
are usually referred to as radiosondes.

Contents

History

In 1924, Colonel William Blaire in the U.S. Signal Corps did the
first primitive experiments with weather measurements from balloon,
making use of the temperature dependence of radio circuits. The
first true radiosonde that sent precise encoded telemetry from
weather sensors was invented in France by Robert Bureau. Bureau
coined the name "radiosonde" and flew the first instrument on
January 7, 1929. Developed independently a year later, Pavel Molchanov
flew a radiosonde on January 30, 1930. Molchanov's design became a
popular standard because of its simplicity and because it converted
sensor readings to Morse
code, making it particularly easy to use without special
equipment or training.[1]

Working with a modified Molchanov sonde, Sergey Vernov was the
first to use radiosondes to perform cosmic ray readings at high
altitude. On April 1, 1935, he took measurements up to 13.6
kilometers using a pair of geiger counters in an anti-coincidence
circuit to avoid counting secondary ray showers.[2][3] This
became an important technique in the field, and Vernov flew his
radiosondes on land and sea over the next few years, measuring the
radiation's latitude dependence caused by the Earth's magnetic
field.

In 1985 the SovietVenus probes Vega 1 and Vega 2 each dropped a radiosonde into the
atmosphere of Venus. The sondes were tracked for two days.

Operation

A rubber or latex balloon filled with either helium or hydrogen lifts the device up through the atmosphere. The maximum altitude to which
the balloon ascends is determined by the diameter and thickness of
the balloon. Balloon sizes can range from 150 grams to 3000 grams.
As the balloon ascends through the atmosphere, the pressure
decreases, causing the balloon to expand. Eventually, the balloon
will expand to the extent that its skin will break, terminating the
ascent. An 800 gram balloon will burst at about 21 kilometres
(69,000 ft).[4] One
rawinsonde from Clark AFB, Philippines reached an altitude of
155,092 feet. At that time USAF was not logging such records.

The modern radiosonde communicates via radio with a computer
that stores all the variables in real-time. The first rawinsondes
were observed from the ground with a theodolite, and gave only a wind estimation
by the position. with the advent of radar by the Signal Corps (United
States Army) it was possible to track the balloons with the SCR-658 radar.
Modern radiosondes can use a variety of mechanisms for determining
wind speed and direction, such as LORAN, radio direction finder, GPS and (in Canada only) Very low
frequency. The weight of a radiosonde is typically 250 grams. It should also be noted that
the average radiosonde is lost and never recovered; however, for
the more expensive instrument packages, balloon bourne unmanned
gliders (or UAVs) are used to ensure
recovery.

Sometimes radiosondes are deployed by being dropped from an
aircraft instead of being carried aloft by a balloon. Radiosondes
deployed in this way are called dropsondes. They are most often used in
special research projects, such as when it is desired to obtain a
profile through a specific feature of a storm.

A list of U.S. operated land based launch sites can be found in
Appendix C, U.S. Land-based Rawinsode Stations[1] of the Federal
Meteorological Handbook #3[2], titled
Rawisonde and Pibal Observations, dated May 1997.

Radiosonde data is a crucially important component of numerical weather
prediction. Because a sonde may drift several hundred
kilometers during the 90 to 120 minute flight, there may be concern
that this could introduce problems into the model initialization.
However, this appears not to be so except perhaps locally in jet stream regions in the
stratosphere [3].